For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningSeat Belt Latch Stop Installation
Preliminary Procedure
Locate the hole in the seat belt webbing where the original seat belt
stop button was located.
If the original hole in the seat belt webbing is not visible, perform
the following:
If either the right or left stop button is missing use the opposing seat
...
Compass
The vehicle may have a compass display in the Driver Information Center (DIC).
The compass receives its heading and other information from the Global Positioning
System (GPS) antenna, StabiliTrak, and vehicle speed information.
Avoid covering the GPS antenna, located on the roof, for long perio ...
Installation Procedure
Note: If the location of the original plug weld holes can not be
determined, space the plug weld holes every 40 mm (1½ in).
Drill 8 mm (5/16 in) for plug welding along the edges of the body rear
end panel as noted from the original panel.
Clean and prepare the attaching s ...